A New Empirical Law for the Prediction of the Zero-Lift Pitching Moment Coefficient of Swept and Tapered Wings

A new empirical law for the prediction of the zero-lift pitching moment coefficient of trapezoidal wings with linear twist and constant taper and sweep in subsonic flow is introduced. This law is quite general in that it does not rely on the use of charts and spans the normal range of values of taper ratio, aspect ratio, and sweep for subsonic aircraft. It does not, however, accommodate different airfoils along the wingspan and only positive sweep has been considered. The empirical law was first derived for the incompressible regime and then an additional empirical law for the compressibility effect has been provided. The results compare favorably with experimental data for straight wings and with some pre-existing empirical methods for wings with low to moderate sweep. It is also shown that the most widely used method of estimating the zero-lift pitching moment coefficient is highly inaccurate